When two devices want to communicate securely, they typically first establish a secure channel. This channel will provide protection for confidentiality, integrity, and/or authentication of the exchanged messages. The method of choice to implement this secure channel is usually based on symmetric cryptography. In that setting, both devices first share a common and secret symmetric key usually called the master key. The master key is typically either predefined at manufacturing time or obtained via public key-based key exchange protocols (for instance elliptic curve Diffie-Hellman). In well-designed secure channels, the master key is never used as-is to encrypt, authenticate, or sign the messages. Instead, the master key is used to generate so-called session keys that are then each dedicated to a particular task (like encryption or authentication) for a limited period of time.